This invention relates generally to polymers and more particularly to polyphenylamide-quinoxalines.
Polyphenylquinoxalines have been described in application Ser. No. 876,572, filed Nov. 13, 1969, entitled, "Phenylated Polyquinoxalines and Method of Preparation Thereof" by Wolfgang J. Wrasidlo, now abandoned. Furthermore, phenylated imide-quinoxaline copolymers are also known and have been disclosed in U.S. Pat. No. 3,642,700 entitled "Phenylated Imide-Quinoxaline Copolymers and Method of Their Preparation" issued to Joseph M. Augl. Additionally, U.S. Pat. No. 3,654,226, entitled "Soluble Imide-Quinoxaline Copolymers" issued to Joseph M. Augl and James V. Duffy and U.S. Pat. No. 3,766,141 entitled "Polyquinoxalines Containing Flexibilizing Groups in the Polymer Chain" issued to Joseph M. Augl and Wolfgang Wrasidlo also disclosed similar types of polymers. As shown by data presented by J. M. Augl and W. Wrasidlo in "Phenylated Polyquinoxalines from 1,4-Bis(phenylglyoxaloyl)benzene," Polymer letters, pp. 281-86 (1969), the polyphenylquinoxalines have better oxidative thermal stabilities than their corresponding unphenylated polyquinoxalines. Additionally, some of these polymers, even those with a relatively high molecular weight, are very soluble in common organic solvents; thus, coatings of these polymers may be coveniently removed from delicate components.
These prior art polyphenylquinoxaline polymers are formed by reacting an aromatic tetraamine, for example, ##STR3## with a bis-benzil such as 1,4-bis-benzil, ##STR4## As disclosed in the above-named patents, a number of aromatic tetramines may be reacted with any of a number of bis-benzils to produce the polyphenylquinoxalines. However, each of those prior art syntheses requires a two component monomer system, and this results in a number of problems and disadvantages. First, if high molecular weight polymers are to be produced, the monomer components must be very pure, accurately weighed, and carefully mixed together. Second, melt polymerization processes are impractical when two or more components having different melting points are required; in this regard, the tetraamines used frequently have high melting points. Third, these two component monomer systems require a solvent in order to insure the homogeneity and stoichiometry of the components and to promote the polymerization reactions. The solvent must be capable of dissolving the monomer components as well as the product polyphenylquinoxaline. Another problem with these prior art processes is that they require residual solvents to insure plasticization and good flow during processing. Removal of these solvents creates voids in the polyphenylquinoxaline polymers, and these voids reduce the strength and thermal stability of the polymers.